Clostophis proboscideus ( Panha & Burch, 2002 )

Tongkerd, Piyoros, Janjai, Teerangkul, Pholyotha, Arthit, Gojšina, Vukašin, Panha, Somsak & Sutcharit, Chirasak, 2025, The microsnail genera Clostophis and Acinolaemus (Eupulmonata, Pupilloidea, Hypselostomatidae) from central Thailand, with description of three new species, ZooKeys 1258, pp. 35-71 : 35-71

Clostophis proboscideus ( Panha & Burch, 2002)

Figs 3 , 4 , 5 , Table 3

Montapiculus proboscidea Panha & Burch, 2002 [1999]: 148, figs 4–7. Type locality: Teppratan mountain, Nakornsawan Province. Panha and Burch 2005: 109, fig. 94.

Clostophis proboscideus — Páll-Gergely et al. 2020: 364 , figs 1 j, 3 b.

Material examined.

Holotype. Thailand • Wat Khao Huai Lung (former Teppratan mountain) , Ban Daen, Banphot Phisai District, Nakhon Sawan Province; 15°55'35.4"N, 99°52'23.2"E; S. Panha leg.; CUMZ 14458 (former Ver-079) . Paratypes. Thailand • 2 shells (Fig. 3 A – C ); same data as for holotype; CUMZ 14457 (former Ver-080) .

Other material.

Thailand • 2 shells (Fig. 4 A – C ); Wat Khao Huai Lung (former Teppratan mountain) , Ban Daen, Banphot Phisai District, Nakhon Sawan Province; 15°55'35.4"N, 99°52'23.2"E; P. Tongkerd leg.; CUMZ 14456 . • 2 shells + 2 juveniles; Wat Tham Bo Ya , Nong Krot, Mueang Nakhon Sawan District, Nakhon Sawan Province; 15°43'49.7"N, 99°56'45.7"E; P. Tongkerd leg.; CUMZ 14465 . • 4 shells + 1 juvenile (Fig. 5 A – D ); Khao Pathawee , Taluk Du, Thap Than District, Uthai Thani Province; 15°28'25.2"N, 99°45'30.3"E; P. Tongkerd leg.; CUMZ 14429 . • 105 shells + 8 juveniles; same collection data as preceding; CUMZ 14463 . • 4 shells; Phu Toei , Huai Khamin, Dan Chang District, Suphan Buri Province; S. Panha leg.; CUMZ 15351 .

Diagnosis.

Shell concave-conical and with long and descending tuba. Apertural dentition with one parietal lamella and one weak palatal plica. Umbilicus wide.

Description.

Shell concave-conical, colourless; growing regularly; last whorl slightly expanded. Shell height 1.7–1.9 mm (including tuba) and shell width 1.6–1.7 mm. Apex large and rounded; protoconch ~ 1 ½ whorls, pitted and with very narrow spiral striae. Whorls ~ 4 ½ – 5 (excluding tuba), rounded and convex; suture wide and deep. Shell surface with strong, elevated and rather equidistant spiral striae (18–22 on body whorl in frontal view), and crossed with weak to strong and irregular radial growth lines. Sometimes growth lines on earlier whorls strong, thus making reticulated surface. Penultimate whorl seemingly sunken into last whorl. Last whorl slightly shouldered to rounded; tuba long, ~ ¼ whorl, strongly descending, curving and slightly twisted. Aperture subovate, open ventrally to subventrally; peristome thin, slightly expanded and with weak depression on parietal side. Apertural dentitions two: parietal lamella relatively strong, high, and situated near apertural lip; palatal plica moderate, low, and situated slightly deeper inside aperture (infrapalatal plica occasionally present). Umbilicus widely opened, occupies ~ ½ of shell width and showing all preceding whorls.

Differential diagnosis.

Clostophis proboscideus differs from C. sankeyi and C. yoga Páll-Gergely & Hunyadi, 2022 by having more numerous and more tightly coiled whorls, lower spire, and wider umbilicus. Meanwhile, C. sankeyi has weaker spiral striations, and C. yoga possesses no apertural dentition, has a narrower umbilicus (<1 / 3 of shell width), and with spiral striations throughout the protoconch ( Benson 1860; Páll-Gergely and Hunyadi 2022; Preece et al. 2022).

Clostophis proboscideus differs from the long and descending tuba morphs of C. multiformis Páll-Gergely & Reischütz, 2020 and C. laidlawi by having a concave-conical shape, wider umbilicus, aperture opening ventrally to subventrally, spiral striations appearing at late stage of protoconch, and with two apertural dentitions (parietal and palatal). In comparison, these two latter species possess conical shells with straight sides, apertures opened sublaterally, narrow umbilicus, and with spiral striations throughout the protoconch. In addition, C. multiformis has only a parietal lamella, while C. laidlawi possesses five apertural dentitions (parietal, angular, upper palatal, lower palatal, and columellar) ( Collinge 1902; van Benthem Jutting 1961; Páll-Gergely et al. 2020).

Distribution.

This species is currently known from several limestone outcrops in central Thailand.

Remarks.

The correct publication date of C. proboscideus has been specified in Jirapatrasilp et al. (2023: 24). This species was described based on three specimens: the holotype and two paratypes. The paratypes are photographed herein, one with a broken palatal wall and the other still intact (Fig. 3 A – C ). However, when we revisited the type locality, we found only two empty shells (Fig. 4 A – C ).

Shell variations were observed from specimens from Khao Patawi, Uthai Thani Province. These specimens possessed a general shell form similar to the type specimens but tended to have wider spaces between radial striations on the last whorl (~ 14–20), and the infrapalatal plica may be present. When an infrapalatal is present, it is located close to a larger plica, and the infrapalatal varies from a noticeable but low ridge (Fig. 5 A ) to weak and inconspicuous (Fig. 5 B, C ) or without an infrapalatal plica (Fig. 5 D ). These variations occur syntopically, and we consider this as intrapopulation variation.

Figures

Figure 3. Clostophis proboscideus, paratype CUMZ 14457 (former Ver- 080) from the type locality. A. Shell from different angles and showing enlarged aperture; B. Protoconch and earlier whorl sculptures; C. Shell from different angles and showing enlarged aperture. Note: the aperture of this shell was broken during the SEM imaging process.

Figure 4. Clostophis proboscideus, topotype CUMZ 14456 from the type locality showing variation in shell shape and sculpture. A. Shell with dense spiral striae sculpture; B. Protoconch and earlier whorl sculptures; C. Shell with conical spire with strong spiral striae and radial ridges.

Figure 5. Clostophis proboscideus, specimen CUMZ 14429 from Khao Pathawee, Uthai Thani Province, intra population variation in basal lamella. A. Specimen with prominent infrapalatal plica; B. Specimen with low but noticeable infrapalatal plica; C. Specimen with inconspicuous infrapalatal plica; D. Specimens without infrapalatal plica. White arrowhead indicates position of infrapalatal plica.